DEVELOPMENT OF VENTRAL PRIMORDIA IN PERVASIVE CILIARY HYPERTROPHY MUTANTS (PCH) OF THE HYPOTRICH CILIATE PARAUROSTYLA-WEISSEI

We studied the development of oral and ventral cirral primordia in dou ble homozygous mlm/pl recessive mutant line 20 and its ''granddaughter '' line 106 expressing pervasive ciliary hypertrophy. The initial loca tion and basal body source for developing oral primordium and fronto-v entro-transverse primordia (FVT) is the same as in wild type (wt) cell s except that their number is higher and variable. The number of FVT s treaks in the mutants are 136-180 percent higher than in wt, the maxim al number of streaks reached 20, whereas 7-8 streaks is the standard f or wt cells. Tn spite of severe overduplication of basal bodies in the FVT streaks the diversification into specific kinds of cirri correspo nds fairly well to the wt pattern. We conclude that the two genes mlm and pl are involved in controlling the extent of basal body proliferat ion in wt cells, and that the site of action of at least the mlm gene includes an event in the cell cycle related to termination of the firs t wave of basal body duplication.